Bug Fixes

Mixed use of AuthenticationMechansimFactory and AccessManager can cause required authentication to be changed during authentication.

Previous changes to X509 certificate support removed SHA256 certificates from x509v3-sign-rsa implementation specified in https://tools.ietf.org/html/draft-saarenmaa-ssh-x509-00 since it was only supposed to support SHA1. Added backwards compatibility -Dmaverick.backwardCompatibleSHA2=true mode to allow implementations to re-introduce this issue if they require the old behaviour

NPE in shutdown when shutdown hook is not set.

DiffieHellman Group Exchange methods fail to return the size requested.